Saturday, 1 June 2013

Detailed Introduction To Computer

The word computer comes from a word "Compute" which means to calculate.Hence,a computer is normally considered to be a calculating device,which that can perform arithmetic operations at enormous speed.In fact the original objective for inventing the computer was to create a fast calculating machine.However,more over 80 % of the work done by computers today is of non-mathematical or non-numerical nature.Hence,To define a computer merely as a calculating device is to ignore over 80% of its function.
More accurately a computer may be defined as a device,which operates upon data.Data can be anything like bio data of various applicants when the computer is used for recruiting personnel,or the marks obtained by various student's in various subjects when the computer is used to prepare result or the detail ( name,age,sex) of various passengers when the computer is employed of making airline of railway reservations,or number of different types in case of use of computers for solving scientific research problems etc.

 Hence data comes in various shapes and sizes,depending upon the types of computer application.A computer can store,process and retrieve data as and what desired.The fact that computer process data is so fundamental that many people have started calling it a data processor.

The name data processor is more inclusive because modern computers not only compute in usual sense,but also perform other functions with the data,which flow to and from them.For example,data processors may gather data from various incoming sources,merge (process of mixing or putting together) them all,sort (process of arranging in some sequence-ascending or descending) them in the desired folder.and finally print the in the desired format.None of these operations involve the arithmetic operations normally associated with the computing device,but the term computer is often applied anyway.

The activity o processing data using a computer is called data processing.Data processing consists of there sub-activities capturing the input data,manipulating the data, and managing the output results.As used in data processing,information is data arranged in an order and form,which is useful to the people who receive it.
Hence,data is the raw material used as input to data processing and information is the processed data obtained as the output of data processing.

Characteristics Of Computer:

The increasing popularity of computer has proved that it is very powerful and useful tool.The power and usefulness of this popular tool are mainly due to it's following properties:

1-Automatic:

A machine is said to be automatic.If it works itself without human intervention.Computers are automate machines because once started on job.they carry on,until the job is finished,normally without any human assistance.However,computer being machines cannot start themselves.They can not go out and find their own problems and solutions.They have to be instructed.That is,a computer works from a program of coded instructions.which specify exactly how a particular job is to be done.Some of the other characteristics of computers,such as speed and accuracy,are due to fact that they are automatic and work on a problem without any human intervention.

2-Speed:

A computer is very fast device.It can perform in few seconds,the amount of work,that a human being can do in an entire year-if he work day and night and did not nothing else.To put it in a different manner a computer does in one minute what would take a man his entire lifetime.
       While talking about the speed of computer,we do no talk in terms of seconds or even milliseconds.Our units of speed are the microseconds,the nanoseconds and even the picoseconds.A powerful computer is capable of performing several billion simple arithmetic operations per second.

3-Accuracy:

In addition being very fast,computers are very accurate.The accuracy of computer is consistently high, and the degree of accuracy of a particular computer depends upon its design.However or a particular computer every calculation is performed with the same accuracy.
Errors can occur in computer.However,these are mainly due to human rather than technological weakness.For example,errors may occur due to imprecise thinking by the programmer (a person who writes instructions for a computer to solve a particular problem) or incorrect input data.Computers errors caused due to incorrect input data or unreliable programs are often referred to as garbage-in-garbage-out(GIGO)

4-Diligence:

Unlike,human beings a computer is free from monotony,tiredness and lack of concentration.It can continuously work for hours,without creating any error and without grumbling.Hence,computers score over human beings in doing routine type of jobs,which require great accuracy.If ten million calculations have to be performed,a computer will perform the ten millionth calculation with exactly the same accuracy and speed as the first one.

5-Versatility:

Versatility is one of the most wonderful thing about computer.One moment it is preparing the results of the examination,the next moment,it is busy preparing electricity bills,and in between,it may be helping an office secretary to trace an important letter in seconds.All that is required to change its talent is to slip in new program (a sequence of instructions for the computer) into it.Briefly a computer is capable of performing almost any task,if the task can be reduced to a series of logical steps.

6-Power of Remembering:

As a human being acquires new knowledge,the brain subconsciously select what it feels to be important worth retaining in its memory and relegates unimportant details to the back of the mind or just forgets them.This is not the case with computers.A computer can sore or recall any amount of information because its secondary storage (a type of detachable memory)Every piece of information can be retained as desired by the user and can be recalled,as and when required.Even after several years,the information recalled would be as accurate as on the day when it was fed to the computer.A computer forgets or looses certain information only when it is asked to do so.Hence, it is entirely up to to the user to take a computer retain or forget a particular information.


7-NO I.Q:

A computer is not a magical device.It possesses no intelligence of its own.Its I.Q is zero at least until today.It has to be told what to do and in what sequence.Hence only the user can determine what tasks a computer will perform.A computer cannot take its own decision in this regard.

8-No Feeling:

Computers are devoid of emotions.They have no feeling and no instincts,because they are machines.Although men have succeeded in building a memory for the computer,but no knowledge and experience we often make certain judgements in our day-to-day-life.However,computers cannot make such judgements on their own.Their judgement is based on the instructions given to them in the form of programs that are written by us.

The Evolutions Of Computer:

Necessity is the mother of invention.The saying holds true for computers also,because computers were invented because of man's search for fast and accurate calculating device.

The first mechanical adding matching was invented by Blaise Pascal in 1642.Later in the year 1671, Baron Gottfried Wilhelm von Leibniz of Germany invented the first calculator for multiplication.Keyboard machines originated in the united States around 1880 and are extensively used even today.Around the period only,Herman Hollerith came up with the concept of punched cards,which were extensively used as input medium in computers even in late 1970s.Business machines and calculators made their appearance in Europe and America towards the end of the nineteenth century.

Charles Babbage,a nineteenth century Professor at Cambridge University,is considered the father of modern digital computers.During his period,mathematical and statistical tables were prepared by a group of clerks.Even the utmost care and precautions could not eliminate human errors.Babbage had to spend several hours checking these tables.Soon he became dissatisfied and exasperated with this type of monotonous job.The result was that he started thinking to build a machine,which could computer tables guaranteed to be error-free.In this process,Babbage designed a "Different Engine"in the year 1822 which could produce reliable tables.In 1842,Babbage came out with his new idea of Analytical Engine,which could produce reliable tables.In 1842, Babbage came out with his new idea of Analytical Engine,which was intended to be completely automatic.It was to be capable of performing the basic arithmetic functions for any mathematical problem and it was to do so at an average speed of 60 additions per minute.Unfortunately,he was unable to produce a working model of this machine,because the precision engineering required to manufacture the machine was not available during that period.However,his efforts established a number of principles,which have been shown to be fundamental to the design of any digital computer.In order to have a better idea of the evolution of computers,let us now briefly discuss about some of the well-known early computers.These are as follows:


1-The Mark 1 Computer (1937-44):

Also known as Automatic Sequence Controlled calculator,this was the first fully automatic calculating machine designed by Howard A. Aiken of Harvard University in collaboration with IBM (International Business Machines)Corporation.Its design was based on the techniques already developed for punched card machinery.It was an electromechanical device,since both mechanical and electronic components were used in its design.

Although machine proved to be extremely reliable.It was very complex in design and huge in size.It used over 3000 electrically actuated switches to control its operations and was approximately 5- Feet long and 8 Feet high.It was capable of performing five basics arithmetic operations :addition,subtraction,multiplication,division and table reference.A number.A number as big as 23 decimal digits could be used in this machine.It took approximately 0.3 second to add two numbers and 4,5 seconds for multiplication of two numbers.Hence,the machine was very slow as compared today's computers.

2-The Atanasoff-Berry Computer (1939-42):

The electronic machine was developed  by Dr.John Atanasoft to solve certain mathematical equations.It was called the Atanasoff-Berry Computer or ABC,after the inventor's name and his assistant,Clifford Berry.It used 45 Vacuum tubes for internal logic and capacitor for storage.

3-The ENIAC (1943-46):

The electronic Numerical integrator and calculator was the first all electronic computer.It was constructed at the Moore School of Engineering of the University if Pennsylvania U.S.A by a design team led by Professors J.Presper Eckert and John Mauchly.

ENIAC was developed because of military need,and was used for many years to solve ballistic problems.It too up the wall space in 20 x 40  square feet room and used 18,000 vacuum tubes.The addition of two numbers was achieved in 200 microseconds and multiplication in 2000 microseconds 4-The EDVAC(1946-52):
A major drawback of ENIAC was that it programs were wired on boards,which made it difficult o change the programs.this problem was later overcome by the "store program"concept introduced by Dr.John Von Neumann.The basic idea behind this concept is that a sequence of instructions,as well as the data,can be stored in the memory of the computer ,from automatically directing  the flow of operations.This feature considerably influenced the development of modern digital computers because of the ease with which different programs can be loaded and executed on the same computer.Due to this feature we often refer to modern digital computers as stored program digital computers.The Electronic Discrete Variable Automatic Computer (EDVAC) was designed on stored program concept.Von Neumann also has a share of the credit for introducing the idea of storing both instructions and data in the binary form (a system that uses only two digits 0 and 1 to represent all characters)instead of the decimal numbers or human readable words.


4-The EDSAC (1947-49):

Almost simultaneously with EDVAC of U.S.A,the Britishers developed the electronic Delay Storage Automatic Calender (EDSAC).The machine executed its program in May 1949.In this machine,addition operation was accomplished in 1500 microseconds and multiplication operation in 4000 microseconds.The machine was developed by a group of scientists headed by Professor Maurice Wikes at the Cambridge University Mathematical Laboratory.


5-The UNIVAC 1 (1951):

The universal Automatic Computer (UNIVAC)was the first digital computer was,which was not "one of a kind".Man UNIVAC machines were produced,the first of which was installed in the Census Bureau in 1951 and was used continuously for 10 years.The first business use of a computer,a UNIVACI was by General Electric Corporation in 1954.
                                               In 1952,the International Business Machines (IBM) Corporation introduced the 701 commercial computer.In rapid succession,improved models of the UNIVAC 1 and other 700 series machines were introduced.In 1953,IBM produced the IBM-650 and sold over 1000 of these computers.
The commercially available digital computers,which could be used for business and scientific applications had arrived.

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